So I've gone through about a dozen different discussions on this topic and finding no solutions, or at least with my amount of Tableau knowledge, I'm lost.

I'm trying to get my data to show the rest of 2018.

There is no data per the "DPU Graph" measure, however, I do have data for the "DPU Targets" for the entire year of 2018, but for whatever reason, I cannot get that data to show up for Aug-Dec 2018. The big whigs here want to see the targets for the rest of 2018, but I have no idea how to give them that.... any experts have a solution to this problem?

It was only a left join to the [DATE] from the main data source. The targets ([Date1] are obviously from a static Excel file. Those are joined in the same exact way as above.

So now everything is in a full outer join.

I've selected "Show missing values", "Show Empty Columns"...

I also took you advice and selected the month from the Target Dates source file. It shows all months now (even though its filtered for 2018)... but no data. Almost there... but dear lord this is frustrating.... ugh.

It's tricky to say without seeing the data. I would try right clicking the data source and "view data" so you can see if the Actuals are coming through correctly in the join. If they are, I would check the filters and then make sure no other data sources are blending in.